In order to establish a connection between connecting connectors or between devices in a correspondence relationship, there is a method to allocate identification information to the connecting connectors. For example, identification information of a first device for connection and identification information of a connection connector disposed at the first device are transmitted to a second device connected through a cable. In the second device, a correspondence relationship between the identification information of the first device and the identification information of the connecting connector disposed at the first device is managed. The second device determines whether or not a pair of the identification information of the first device and the identification information of the connecting connector disposed at the first device is matched with the correspondence relationship. If it is no matched, it is determined that it is connected to a device or a connecting connector that is not a target (for example, see Patent Literature 1).